Involvement of phenoxyl radical intermediates in lipid antioxidant action of myricetin in iron-treated rat hepatocyte culture.

Supplementation of rat hepatocyte cultures with the flavonoid myricetin (300 microM) led to the formation of phenoxyl radical intermediates, as detected in intact cells by electron paramagnetic resonance (EPR) spectroscopy. These radicals corresponded to one-electron oxidation products of myricetin. The level of phenoxyl radicals was significantly reduced when myricetin-treated hepatocyte cultures were also supplemented with iron (Fe-NTA 100 microM). This suggested that iron could accelerate the oxidation flux of myricetin. Moreover, myricetin was found to be able to inhibit lipid peroxidation induced by iron in hepatocyte culture. Free malondialdehyde (MDA) levels and the amount of radicals derived from oxidized lipids were greatly reduced when myricetin was added to iron-treated cultures. This showed that myricetin was a good inhibitor of lipid peroxidation in this model and that the intermediate generation of phenoxyl radicals might contribute to the antioxidant mechanism of myricetin.